Monitors

The most important output devices, where we can see immediately our graphics results, are monitors.
Because their development did not lag behind that of any other information technologies, we can state that
for a reasonable price we can get a quality monitor. Despite the fast development and increases in
LCD monitor production volumes, the basic element in the field of monitors remains the cathode
ray tube (CRT) monitor.

The majority of classical display monitors are based on the principle of the cathode screen.
This screen is based on an emitting cathode and a phosphor screen. In creating a display,
the emitting cathode emits a beam of rays which passes through focusing electrode systems,
and then it is swept through an electromagnetic field to the monitor screen, where it emits a
weakening light. For keeping a quality image, it continual renewal is necessary. This is called
as monitor renewal frequency. Sweeping is the result of two pairs of electrodes, moving
the electron beam in the horizontal and in the vertical directions concurrently. To form a color
image, we need three cathodes, a special luminescent layer, and a
screen mask. On the screen,
there are regularly spread three luminescent points, representing individual components of RGB.
These three points appear for the human eye as only one resulting point.

As a standard, the sweeping electrodes use a 90-degree angle of sweeping. Some of the latest
models, use also a 100-degree angle, which enables a reduction in overall dimensions, but on
the other hand, brings higher requirements for displaying.

In the contrast to LCD monitors where the given diagonal sets the dimension of a monitor, in classical monitors
the 17-inch monitor only rarely exceeds 16 inches, and a 15-inch unit has in fact only about 13.8 up to 14.1 inches,
a 17-inch one about 15.7 up to 16.2 inches, and a 14-inch model is about 13.3 inches.

For determining the renewal frequency is important the value of the horizontal frequency
given in kHz (kilo Hertz),
which gives the number of lines per second which can be drawn on the given monitor.

The value of the vertical frequency means what frequency the monitor can deal with.

Example : Calculation of the frequency of the monitor with horizontal frequency 70 kHz with the resolution 1024x768.

The number of displayed lines is 768. The beam can draw 70 000 lines, because the transition to another line takes about 7 percent
(this value is approximate, and with every monitor type it depends on the producer of the relevant monitor), so the resulting frequency is:

Resulting frequency = (70 000 * 0.93 ) / 768 = 85 Hz

Maximum renewal frequency

For a monitor with the given horizontal frequency in the given resolution

Horizontal frequency

640x480

800x600

1024x768

1280x1024

1600x1200

30 kHz

58 Hz

46 Hz

36 Hz

27 Hz

23 Hz

35 kHz

67 Hz

54 Hz

42 Hz

32 Hz

27 Hz

40 kHz

77 Hz

62 Hz

48 Hz

37 Hz

31 Hz

45 kHz

87 Hz

70 Hz

54 Hz

41 Hz

35 Hz

50 kHz

97 Hz

78 Hz

60 Hz

46 Hz

39 Hz

55 kHz

106 Hz

85 Hz

67 Hz

51 Hz

43 Hz

60 kHz

116 Hz

93 Hz

73 Hz

55 Hz

47 Hz

65 kHz

126 Hz

101 Hz

79 Hz

60 Hz

51 Hz

70 kHz

136 Hz

109 Hz

85 Hz

65 Hz

55 Hz

75 kHz

145 Hz

117 Hz

91 Hz

69 Hz

59 Hz

80 kHz

155 Hz

125 Hz

97 Hz

74 Hz

63 Hz

85 kHz

165 Hz

133 Hz

103 Hz

79 Hz

67 Hz

90 kHz

175 Hz

141 Hz

110 Hz

83 Hz

71 Hz

95 kHz

185 Hz

148 Hz

116 Hz

88 Hz

75 Hz

100 kHz

194 Hz

156 Hz

122 Hz

93 Hz

80 Hz

105 kHz

204 Hz

164 Hz

128 Hz

97 Hz

84 Hz

110 kHz

214 Hz

172 Hz

134 Hz

102 Hz

88 Hz

115 kHz

224 Hz

180 Hz

140 Hz

107 Hz

92 Hz

120 kHz

233 Hz

188 Hz

146 Hz

112 Hz

96 Hz

125 kHz

243 Hz

196 Hz

153 Hz

116 Hz

100 Hz

130 kHz

253 Hz

203 Hz

159 Hz

121 Hz

104 Hz

Note:
These values are only an example of which frequencies a monitor uses in the case of a given resolution.
In no case can you expect that a 14-inch monitor with 30 kHz can run in the resolution 1600x1200 with 23 Hz.
Real renewal frequencies depend on the given monitor.

18.5.2 Categorization of CRT monitors by mask type

At present, we can meet with three types of mask in CRT monitors.

Cathode display with dot mask.
Most frequently is used a display with a dot mask. In front of the screen there is a dotted invar foil where display points are separated.
The quality of the resulting image is proportional to the distance of the dots in this mask. The lower the distance, the better quality the image.
Currently this distance is in the range 0.25 ? 0.28 mm.

Cathode display with the slot grid .
Newer types of display use a grid with pre-stressed wires in the vertical direction.
To ensure the stability of this sort of grid, there are two wires whose shades are apparently visible in the display.
This type of design is used in monitors like: SONY, TRINITRON, and MITSUBHITSHI DIAMONDTRON.
Their advantage is the excellent quality of colors and higher contrast and brightness

Cathode display with slot mask . The new display combines a slot grid with a dot mask.

18.5.3 What minimum requirements a monitor should fulfill

When buying a new monitor, you should in the first place realize that in working with it your eyes are in a game.
Accordingly, if we have a good quality monitor, your eyes do not get tired so quickly and strained.
Therefore don't skimp, invest in a high quality monitor. It should comply with the following requirements:
in the working resolution a renewal frequency of at least 85 Hz plus some of the certificates
MPR-II, TCO' 95, TCO' 99, and EPA EnergyStar. The image should be quality, stable, and not
blinking, small distances between points (0.28 mm good, 0.26 mm excellent, 0.24 mm the best),
moir? control, digital control, on screen menu (OSM), and horizontal frequency: with a 15-inch model
of at least 70 kHz, with a 17-inch model at least 86 kHz, with a 19-inch model at least 96 kHz.

18.5.4 What is the most appropriate resolution for monitors.

The important criterion is the real resolution that can be used in a given monitor in relation to its diagonal.

Display size

640x480

800x600

1024x768

1280x1024

1600x1200

14''

Recommended

Useable

Unusable

Unusable

Unusable

15''

Useable

Recommended

Exceptional

Unusable

Unusable

17''

Useable

Useable

Recommended

Useable

Unusable

19''

Useable

Useable

Recommended

Recommended

Useable

21''

Useable

Useable

Useable

Recommended

Useable

In conclusion: Do not use the monitor in a resolution other than those recommended, even if only
to a limited extent, otherwise you can overfatigue your eyes.

18.5.5 Radiation and ergonomics

VGreat attention is paid to the damaging effects
of monitors on humans. In the course of working at a PC often there are headaches
and deterioration of sight. These problems are due to the wrong working environment
and wrong setting of the display system.

Some practical advice:

Place great importance on the correct layout of surrounding light sources reflecting
off the monitor and diminishing the readability of the text

Use the recommended resolution for a given monitor

Renewal frequency at least 85 Hz

Radiation load in front of the monitor :

Range of monitor radiation

Standard as per. MPR II

Standard as per TCO 95

Electric field V/m 5 Hz ? 2 kHz

25

10

Electric field V/m 2 kHz ? 400 kHz

2,5

1

Magnetic field V/m 5 Hz ? 2 kHz

250

200

Magnetic field V/m 2 kHz ? 400 kHz

25

25

Radiation load in an environment :

Environment

Underground garage

Railway station in Munich

Apartment in Munich

Forest

Electric field V/m 5 Hz ? 2 kHz

2

6.5

32

<0.1

Electric field V/m 2 kHz ? 400 kHz

<0.1

0.5

<0.1

<0.1

Magnetic field V/m 5 Hz ? 2 kHz

450

470

150

<5

Magnetic field V/m 2 kHz ? 400 kHz

<0.1

0.2

<0.1

<0.1

The most important point with ergonomics evaluation is the maximum frequency of image renewal
in various resolutions. The main requirement is a uniform shining display, without blinking or flickering
of the image. The second parameter is the anti-reflection feature of the surface of the display.
A quality monitor must have a stable display in transits from clear into dark picture, while replaying
a video and clear switching in the course of changing the resolution of the screen.

18.5.6 Terms and abbreviations

CRT (Cathode Ray Tube): the cathode ray tube is used in classical monitors.
The picture is formed through a continually renewed electron beam on a screen covered by a luminescent material

Degaussing (or de-magnetizing): removal of any
distortion due to magnetizing the screen.

Color temperature: defines character of white color established
on the screen of the display through the rate of basic colors ? red, green, and blue.

Convergence (taper):
controlling rays of the basic color so that they establish with line. Errors in this feature result in a worsening sharpness
and color hues mainly in white lines.

LCD (Liquid
Crystal Display): (liquid crystal display): flat displays based on using changes in the optical features of so-called
liquid crystals in relation to the changes of an electric field acting upon them

Moire:
nunwanted disturbing patterns of a wave character due to interference between image elements, the defined image signal, and the
actual decomposition of image elements defined on the retina via the mask or the grid of the display.

Renewal frequency of the image
(often only 'refre') determines the number of complete renderings of the image per second.

Spacing of image points
is the smallest diagonal distance between image points of the same color; at present gap spacing is
given also for the horizontal which are smaller and comparable to the spacing of a strip of the same color,
given for a screen with an aperture grid.

VESA
(Video Electronics Standards Association), is the organization dealing with standards for video and
communication between the monitor and the graphical card.

TCO
There is frequently seen a sticker on monitors stating 'TCO95' or 'TCO99'. What in fact does this logo mean?
It is the certificate of an organization (Swedish Trade Unions),
http://www.tco-info.com) in cooperation with the
Swedish Nature Protection organization and NUTEK (National Swedish Commission for Industrial Development)
who appraise the relationship of a given monitor (or other device) to the environment and health of the user.
Gradually, there have been established the following standards: MPR I (1990). MPR II (1991), TCO 92 (1992),
TCO 95 (1995), TCO (1998). The better the monitor complies with a standard the better quality of the monitor.
Today, the minimum requirement is that monitors should comply with the standard TCO 95.